Continuous fiber-reinforced thermoplastic resin composite material is a composite material using an impregnation device to impregnate and reinforce a continuous fiber with a molten resin. Compared with a short fiber-reinforced thermoplastic resin composite material, the continuous fiber-reinforced thermoplastic resin composite material has advantages such as a high strength, a good impact resistance and a stable dimension, and thus has extensive application in fields such as automobile, aerospace electronics and electrical appliances, mechanical equipment, weaponry industry, construction equipment, furniture, gymnastic apparatus and the like.
In a process of melt impregnation, a flow of a resin melt in a fiber bundle takes place both in an axial direction and a radial direction of the fiber, similarly regarding as a fluid flowing in a porous medium, according to the Darcy law:
  μ  =            dx      dt        =                  kΔ        ⁢                                  ⁢        P                    η        ⁢                                  ⁢        Δ        ⁢                                  ⁢        x            
wherein, μ is an permeation rate, k is an permeation coefficient, ΔP is a pressure drop that the fluid acts on the porous medium, η is a fluid viscosity, and Δx is a melt flow distance. It can be known that increasing a melt pressure, reducing a thickness of the fiber bundle and decreasing a melt viscosity can increase an impregnation rate.
For example, CN106113317A discloses an apparatus for a continuous carbon fiber melt impregnating a thermoplastic polymer. An interval between an upper die and a lower die of the impregnation mold forms a melt pool. Between the upper die and the lower die, curved surfaces matching with each other are provided, and three sets of powered roller pair are also provided. A tension roller is provided between the roller pair. Squeezing a resin melt by the roller pair provides the resin melt with an impregnating pressure. Also CN105058817A discloses an apparatus for a continuous long fiber reinforcing a thermoplastic resin sheet material. Gear sets meshing with each other are provided above and below the fiber bundle, to enhance the flow of the melt on the fiber bundle in each direction. Additionally, CN104827686A discloses an impregnation apparatus for plant fiber and a method thereof. A plurality of compression roller sets of which a tension can be adjusted are used to squeeze the impregnated fiber, in order to provide an impregnating pressure to the impregnation of the resin melt. The three patent applications disclosed above can achieve a relatively ideal impregnating effect in the case of a low drawing speed and a low concentration of the resin melt. However, when the continuous fiber goes through these narrow impregnation channels with a curved shape or a wave shape, since a relatively large flow velocity difference exists inside the resin melt, a velocity gradient of the resin melt would form a shearing field. When the impregnation is performed in a condition of high drawing speed, a broken yarn is caused easily. When a viscosity of the resin melt is high, the broken yarn would further be aggravated enormously. Besides, since a relatively large number of rotating rollers or gears present inside the impregnation area, a complicated structure of equipment and difficult cleaning and maintenance are caused. In the case of the broken yarn in the fiber bundle, the fiber bundle is easy to enwind the rotating rollers or gears, aggravating the broken yarn.